WASHINGTON—A document compiled by Democrats on a Senate committee levels new allegations against Ronny Jackson, President Donald Trump’s embattled nominee to head the Department of Veterans Affairs, who said Wednesday he will keep fighting for the job despite a growing list of accusations including charges of reckless drug-dispensing practices.

Dr. Jackson, speaking briefly Wednesday with reporters at the White House, rejected one of the most serious allegations contained in the report—that he wrecked a government vehicle after getting drunk at a Secret Service going-away party. “I did not wreck a car,” he said. “That should be pretty easy to prove.”

Read More

He said he was “still moving ahead as planned” with the nomination. Dr. Jackson, a Navy rear admiral, has been White House physician under three administrations.

The compilation of allegations by the Democratic staff on the Senate Veterans Affairs Committee, which was assembled from accusations by roughly two-dozen current and former colleagues of Dr. Jackson, said that he had private stocks of controlled substances and suggested that he took advantage of lax record-keeping of drug inventories in the White House medical unit.

Once, missing Percocet threw the medical staff into a panic, the report found. It was revealed later that Dr. Jackson had provided a large supply to a staffer in the White House military office, the report said.

The report said Dr. Jackson also asked staffers to write prescriptions for each other so that drugs could be given to non-beneficiaries. It said physicians felt so uncomfortable that they refused to be part of the culture of loose distribution of drugs to current and former White House staffers—and, at times, their family members.

The new revelations emerged as the White House was defending its nominee. Officials had asked the Senate to reschedule a confirmation hearing that lawmakers postponed amid concerns over past performance and behavior.

Administration officials described President Donald Trump as “bewildered” and “surprised” by the response to Dr. Jackson’s nomination, while acknowledging that prior vetting of the nominee could have helped stave off problems. Officials described the president as so far skeptical of the allegations against his physician, whom many people close to the administration described as very well liked in the White House.

The report also repeated charges that the committee’s top Democrat, Jon Tester of Montana, had circulated one day earlier: that Dr. Jackson prescribed the sleep aid Ambien and a separate wake-up drug called Provigil on overseas flights without documenting recipients’ medical histories. Both drugs are controlled substances, the report said, and require tracking, the report said. Dr. Jackson’s practices were so blatant that he was known as “the candy man” because he could provide whatever drugs anyone wanted without paperwork, the report said.

Former administration officials and lawmakers said it isn’t unusual to take Ambien and other sleep-related drugs on foreign trips to help navigate new time zones. In his briefing in January on the president’s health, Dr. Jackson told reporters the president takes Ambien “on occasion, like we all do, on overseas travel.”

“When we travel from one time zone to another time zone on the other side of the planet, I recommend that everyone on the plane take a sleep aid at certain times so that we can try our best to get on the schedule of our destination,” Dr. Jackson said.

“People take Ambien to help them transition through time zones—it’s pretty common I’m led to believe,” said Sen. John Cornyn (R., Texas).

One former official who worked in the Obama White House said he never saw Dr. Jackson offering Ambien to staff, though the doctor would prescribe medication for aides who needed it, consistent with his role as White House physician.

This person said he once asked Dr. Jackson for an Ambien to help him sleep and the doctor prescribed one.

The ex-Obama official said he never saw Dr. Jackson drink any alcohol. He described Dr. Jackson as a well-liked figure in the Obama White House who would on occasion play in Mr. Obama’s pickup basketball games.

The White House on Wednesday prepared to mount a “full-throated defense” of Dr. Jackson, one administration official said. Marc Short, the White House’s legislative affairs chief, said Wednesday that the White House would be “asking for the opportunity to be able to tell his story.” One administration official said the White House plans to mobilize people who have worked with Dr. Jackson, as well as veterans’ groups who support his troubled nomination.

The Republican National Committee is assisting the White House, crafting talking points for supporters and preparing a rapid-response operation, according to a person familiar with the matter. The talking points are expected to say that Dr. Jackson is being unfairly targeted and to highlight his military record.

The report paints a picture of a culture in which drugs could be prescribed without going through proper procedures. It refers to “loose dispensing of drugs” in which Dr. Jackson prescribed substances without proper paperwork. It says one physician said Dr. Jackson “has been lucky because his prescribing practices are reckless.”

Once, a prescription for a sleeping aid was written for a provider instead of for the actual beneficiary in order to protect the beneficiary’s identity.

Because of missing documentation, one provider was put in a difficult spot when prescribing medication because he or she couldn’t know what other drugs a particular patient might be taking, according to the summary.

Lawmakers already were guarded about the choice of Dr. Jackson and whether his background as White House physician prepared him to lead a bureaucracy of 370,000 employees.

Asked about whether the White House looked into Dr. Jackson’s background before the nomination, White House press secretary Sarah Sanders on Wednesday said he had received “more vetting than most nominees.” She added that four separate investigations into his conduct, including one by the Federal Bureau of Investigation, didn’t uncover any of the allegations raised during the Senate’s confirmation review.

“There has been no area of concern that was raised for Dr. Jackson specifically,” Ms. Sanders said.

Senators said one document they want to see is a 2012 audit by the U.S. Navy’s Bureau of Medicine and Surgery that described a difficult workplace environment in the White House medical office.

“We have not been told we will get it, but we damn well need it” Mr. Tester said.

In his response to the audit, Dr. Jackson said that morale was far better than the report depicted.

The White House released an audit from the following year, 2013, that showed healthy majorities of medical-unit staff felt “valued” and agreed that the work atmosphere had improved.

The chairman of the Veterans Affairs Committee, Johnny Isakson (R., Ga.), said Wednesday he was prepared to move forward with a hearing on Dr. Jackson but indicated that the White House first needed to provide the necessary documents.

“He deserves a hearing and he’s going to get it,” Mr. Isakson told reporters. “We’re waiting for the documents and when we get them we’ll move forward.”

Despite the allegations, Mr. Tester did not rule out the possibility that Dr. Jackson could still be confirmed.

Some administration officials believe the drama surrounding Dr. Jackson’s nomination could have been avoided through proper vetting.

“Vetting has always been an issue with nominees,” an official said, describing the president’s habit of tweeting his decisions before alerting the press office as “standard operating procedure.”